Avalanche Forecast

Issued: Jan 7th, 2020 4:30PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada astclair, Avalanche Canada

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A rapid, critical load has been added to the snowpack. Touchy conditions with high consequences will be widespread on Wednesday. Travel in avalanche terrain is not recommended.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Tuesday night: Cloudy, 20-30 cm of snow, moderate southwest wind, alpine temperature -4 C.

Wednesday: Cloudy, snow tapering by noon with 5-10 cm of accumulation, moderate west wind, alpine temperature -9 C.

Thursday: Partly cloudy, isolated flurries with trace accumulations, light west wind, alpine high temperature -10 C.

Friday: Cloudy, 5-15 cm of snow, moderate south wind, alpine high temperature -10 C. 

Avalanche Summary

There have been many reports of large (size 2-2.5) avalanches from both natural and human triggers on a variety of aspects and elevations releasing on surface hoar layers formed in late December. These avalanches have been breaking 60-90 cm deep. Several of them have been remote-triggered.

As the new snow settles, storm slab avalanches are likely to be triggered and have the potential to step down to these deeper layers, forming very large and destructive avalanches.

Snowpack Summary

Up to 60 cm of new snow is forecast to accumulate by Wednesday afternoon with moderate to strong southwest wind. This will form a new storm slab problem that will need to be managed conservatively. Expect areas where the snow is being drifted by wind to be more reactive. 

Two layers of surface hoar from late December are now buried 60-120 cm deep. These layers continue to produce large avalanches across aspects and elevations. Small avalanches in the new snow have the potential to step-down to these persistent weak layers.

Terrain and Travel

  • Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
  • Be careful to keep storm day fever from luring you out into bigger terrain features.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

40-60 cm of snow is forecast to accumulate in the region forming new, reactive storm slabs. There is potential for storm slabs to step down to deeper weak layers, forming large and destructive avalanches. Storm slabs will be more pronounced in lee terrain features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs

Two layers of surface hoar from late December are now buried 60-120 cm deep. These layers have produced many large avalanches across aspects and elevations with incremental loading from new snow and wind. Significant loading from new snow has the potential to bring these weak layers to their tipping point and to create conditions for step-down avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Jan 8th, 2020 5:00PM

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